Vehicle battery pack ballistic shield

ABSTRACT

An improved protection system for a battery pack mounted between the passenger cabin floor panel of an electric vehicle and the driving surface is provided, the system utilizing a ballistic shield mounted under the electric vehicle and interposed between the battery pack enclosure and the driving surface, where the ballistic shield is spaced apart from the enclosure bottom panel. A layer of a compressible material may be interposed between the ballistic shield and the battery pack enclosure.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 13/311,343, filed 5 Dec. 2011, and claims benefit of the filingdate of U.S. Provisional Patent Application Ser. No. 61/426,254, filedDec. 22, 2010, the disclosures of which are incorporated herein byreference for any and all purposes.

FIELD OF THE INVENTION

The present invention relates generally to vehicle structures and, moreparticularly, to means for improving the integration of a battery packinto an electric vehicle.

BACKGROUND OF THE INVENTION

A large percentage of the world's vehicles run on gasoline using aninternal combustion engine. The use of such vehicles, more specificallythe use of vehicles which rely on fossil fuels, e.g., gasoline, createstwo problems. First, due to the finite size and limited regionalavailability of such fuels, major price fluctuations and a generallyupward pricing trend in the cost of gasoline are common, both of whichcan have a dramatic impact at the consumer level. Second, fossil fuelcombustion is one of the primary sources of carbon dioxide, a greenhousegas, and thus one of the leading contributors to global warming.Accordingly, considerable effort has been spent on finding alternativedrive systems for use in both personal and commercial vehicles.

Electric vehicles, due to their cleaner and more efficient drivesystems, offer one of the most promising alternatives to vehicles thatuse internal combustion drive trains. To be successful, however, anelectric vehicle must meet consumers' expectations relative toperformance, range, reliability, lifetime and cost. These expectations,in turn, place considerable importance on the design, configuration andimplementation of the electric vehicle's rechargeable batteries.

In a typical electric vehicle, either an all-electric or hybrid vehicle,the battery pack is mounted to the vehicle's floor in a locationintended to be as unobtrusive as possible. For example, in U.S. Pat. No.7,427,093, issued 23 Sep. 2008, the battery pack is mounted to thevehicle floor panel, under the front seat. The disclosed system includesa protective member, for example attached to the battery pack itself,which is shaped and positioned to protect the battery pack and thewiring harness from possible damage by passengers in the rear seat.

U.S. Pat. No. 7,717,207, issued 18 May 2010, discloses an alternatebattery pack mounting structure that is intended to minimize batterypack damage in the event of a vehicle collision. As disclosed, thebattery pack is mounted to the rear portion of the vehicle frame, theframe including a deformable portion that deforms in an up-downdirection when an impact load is applied in a longitudinal direction.The battery pack is fixed to the frame in such a way that it will moverelative to the deformable portion when the deformable portion deformsunder load, thus minimizing the transfer of load energy to the batterypack and allowing the shape of the pack to be maintained during acollision.

U.S. Pat. No. 8,037,960, issued 18 Oct. 2011, discloses an alternatebattery mounting structure designed to minimize battery pack damage inthe event of a vehicle collision. As disclosed, the battery packstructure is mounted to the rear side of the rear vehicle seats usingbolts/screws that are designed to break and allow the battery pack todetach and move when the vehicle is in a collision.

Although the prior art teaches a variety of techniques for mountinglarge battery packs within an electric vehicle, what is needed is abattery mounting system that fully integrates the battery pack enclosureinto the vehicle in such a way as to take advantage of the pack'srigidity and strength, while still protecting the battery pack fromaccidental damage and minimizing the effects of the battery pack onvehicle occupant comfort and safety. The present invention provides sucha system.

SUMMARY OF THE INVENTION

The present invention provides a system for protecting a battery packmounted to an electric vehicle, the system utilizing a battery packenclosure that includes an enclosure top panel, an enclosure bottompanel, and a plurality of enclosure side members, where the battery packenclosure is configured to hold a plurality of batteries, and where thebattery pack is mounted between the passenger cabin floor panel and thedriving surface. The system further includes a ballistic shield mountedunder the electric vehicle and interposed between the battery packenclosure and the driving surface, where the ballistic shield is spacedapart from the enclosure bottom panel by at least 5 millimeters;alternately, by at least 10 millimeters; alternately, by at least 15millimeters; alternately, by at least 25 millimeters; alternately, by atleast 35 millimeters; alternately, by at least 50 millimeters. Theballistic shield may be fabricated from aluminum, an aluminum alloy,steel, fiberglass, a carbon fiber/epoxy composite, and/or plastic.

The battery pack enclosure may be substantially airtight; may befabricated from an aluminum, aluminum alloy or steel; may have theenclosure bottom panel welded, brazed, soldered or bonded to theplurality of enclosure side members; may have the enclosure top panelbolted to the plurality of enclosure side members; may be positionedbetween the front and rear vehicle suspension assemblies and mountedbetween, and mechanically coupled to, vehicle structural members (e.g.,rocker panels) located on either side of the vehicle; and may include aplurality of cross-members that transverse the battery pack enclosureand segregate the batteries into groups of batteries.

In another aspect of the invention, the system may further comprise aplurality of stand-offs interposed between the ballistic shield and theenclosure bottom panel, where the stand-offs are coupled to the outersurface of the enclosure bottom panel adjacent to mounting locations ofcross-members within the battery pack enclosure.

In another aspect of the invention, the system may further comprise alayer of compressible material interposed between the ballistic shieldand the battery pack enclosure, where the compressible material maydeform in an elastic manner, or in an inelastic manner, uponcompression. The compressible material layer may be fabricated from foamor plastic. The compressible material layer may be shaped, for examplewith a plurality of projections and a plurality of dips (e.g., egg crateshaped).

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a perspective view of a portion of a vehicle body andframe with the battery pack separated from the structure;

FIG. 2 provides a perspective view of a vehicle's undercarriage with thebattery pack incorporated into the vehicle structure;

FIG. 3 provides a simplified bottom view of an electric vehicle with abattery pack incorporated into the vehicle structure;

FIG. 4 provides a perspective view of a battery pack to rocker panelassembly;

FIG. 5 provides a perspective view of the battery pack shown in FIGS.1-4;

FIG. 6 provides a perspective view of the battery pack shown in FIGS.1-5, with the top panel removed;

FIG. 7 provides a perspective view of the battery pack shown in FIGS.1-6, this view showing three of the battery modules in place within thepack;

FIG. 8 provides a perspective views of a single battery module for usewithin the battery pack shown in FIGS. 1-7;

FIG. 9 illustrates the battery module shown in FIG. 8 with the uppermodule components removed;

FIG. 10 illustrates the battery module shown in FIGS. 8 and 9 with thecells removed;

FIG. 11 provides a perspective, cross-sectional view of the battery packshown in FIGS. 1-7 mounted under the floor panel of the vehicle shown inFIG. 1;

FIG. 12 provides a detailed cross-sectional view of a portion of thebattery pack along with the structures immediately above and below thebattery pack enclosure;

FIG. 13 illustrates a modification of the embodiment shown in FIG. 12 inwhich two different layers are interposed between the top of the batterypack enclosure and the underside of the vehicle floor panel;

FIG. 14 illustrates a modification of the embodiment shown in FIG. 12 inwhich a compressible material is interposed between the battery pack andthe ballistic shield; and

FIG. 15 illustrates a modification of the embodiment shown in FIG. 12 inwhich a shaped compressible material is interposed between the batterypack and the ballistic shield.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In the following text, the terms “battery”, “cell”, and “battery cell”may be used interchangeably and may refer to any of a variety ofdifferent cell types, chemistries and configurations including, but notlimited to, lithium ion (e.g., lithium iron phosphate, lithium cobaltoxide, other lithium metal oxides, etc.), lithium ion polymer, nickelmetal hydride, nickel cadmium, nickel hydrogen, nickel zinc, silverzinc, or other battery type/configuration. The term “battery pack” asused herein refers to multiple individual batteries contained within anenclosure, the individual batteries electrically interconnected toachieve the desired voltage and capacity for a particular application.As such, the terms “battery pack” and “battery pack enclosure” may beused interchangeably herein. The term “electric vehicle” as used hereinmay refer to an all-electric vehicle, also referred to as an EV, aplug-in hybrid vehicle, also referred to as a PHEV, or a hybrid vehicle,also referred to as a HEV, where a hybrid vehicle refers to a vehicleutilizing multiple propulsion sources one of which is an electric drivesystem.

In accordance with the present invention, and as illustrated in FIGS.1-3, a battery pack 101 is mounted under the floor panel of an electricvehicle 100. Preferably the battery pack is integrated within thevehicle's structural frame, thus utilizing the battery pack's inherentrigidity and strength to enhance the overall performance and impactresistance of vehicle 100. In the illustrated embodiment, battery pack101 not only transverses the width of the vehicle, i.e., from rockerpanel to rocker panel, but also extends most of the distance between thefront suspension 201 and the rear suspension 203. It will be appreciatedthat while smaller battery packs mounted under the vehicle's floorpanel(s) may be used with the invention, such smaller packs willtypically not provide the same level of vehicle performance enhancementas that provided by the preferred battery pack. In the illustratedembodiment, battery pack 101 is approximately 2.7 meters long and 1.5meters wide and has a thickness that varies between approximately 0.1meters to 0.18 meters, the thicker dimension applicable to thoseportions of the battery pack in which battery modules are stacked one ontop of another.

As noted above, preferably battery pack 101 is configured to transversethe width of the vehicle and be coupled to the rocker panels located oneither side of the vehicle. FIG. 4 illustrates the attachment of batterypack 101 to a rocker 401, this figure showing the location of batterypack 101 under vehicle floor panel 403. Preferably rocker 401 isextruded, for example using an aluminum or aluminum alloy extrusion asdescribed in detail in co-pending U.S. patent application Ser. No.13/308,206, filed 30 Nov. 2011, and attached to the battery as describedin co-pending U.S. patent application Ser. No. 13/308,300, filed 30 Nov.2011, the disclosures of which are incorporated herein for any and allpurposes. In general and as illustrated for the preferred embodiment,battery pack enclosure 101 includes side members 405 that include anextended mounting flange, or region, 407 that is positioned under rocker401. Region 407 is perforated in order to allow passage of a pluralityof mounting bolts 409. Mounting bolts 409, in combination with nuts 411,mechanically couple extended region 407 of battery pack 101 to rocker401. To simplify assembly, channel nuts 411 are held in place duringvehicle assembly using a channel nut retainer 413. Retainer 413 ispositioned within rocker 401 using internal feature 415, therebysimplifying vehicle assembly and reducing manufacturing costs. It willbe understood that other techniques may be used to mount the batterypack under the vehicle's floor panel.

FIG. 5 provides a perspective view of battery pack 101 with the topenclosure panel 501 in place, panel 501 preferably providing asubstantially airtight seal. Side structural elements 405, which arepreferably hollow or include multiple cavities, are also visible as isbattery pack mounting flange 407 that is used to mechanically andthermally couple the battery pack enclosure to the vehicle structure(not shown in this figure). FIG. 6 shows battery pack 101 with topmember 501 removed, this view showing multiple cross-members 601A-601H.The number of cross-members is based on the number of cells/cell modulesthat are to be encased within the battery pack as well as the desiredstructural characteristics of the battery pack. Preferably battery packside members 405, including extended regions 407, battery pack top panel501, battery pack bottom panel 603 and cross-members 601A-601H are eachfabricated from a light weight metal, such as aluminum or an aluminumalloy, although other materials such as steel may be used for some orall of the battery pack components. Bottom panel 603 may be welded,brazed, soldered, bonded or otherwise attached to side members 405, withthe resultant joint between panel 603 and member 405 preferably beingsubstantially air-tight as well as being strong enough to allow bottompanel 603 to support the batteries contained within the pack. Top panel501 is typically attached to members 405 using bolts or similar means,thus simplifying battery replacement as well as allowing batteryinterconnects, battery pack components, cooling system components andother battery pack components to be repaired and/or replaced.

Cross-members 601A-601H provide several benefits. First and foremost,cross-members 601A-601H provide mechanical and structural strength andrigidity to the battery pack and to the vehicle to which the batterypack is attached. Additionally, cross-members 601A-601H help tosegregate thermal events by providing a thermal barrier between groupsof cells as well as minimizing gas flow between sections 605, sections605 being defined by the cross-members, side members 405, top member 501and bottom member 603. By segregating thermal events within smallergroups of cells, thermal runaway propagation is limited as is thepotential for battery pack damage.

FIG. 7 shows a similar view to that provided by FIG. 6, with theinclusion of a couple of cell modules 701. In this illustration, asingle module 701 is shown positioned within one of the seven, largersections 605 of battery pack 101. Note that in the illustratedembodiment, each large section 605 is designed to house a pair ofbattery pack modules 701. Additionally, in this illustration there aretwo modules 701 stacked one on top of the other in the front section 607of pack 101. Note that in the preferred embodiment, each module 701contains 370 individual cells, each cell utilizing an 18650 form factor.It should be understood, however, that this configuration is onlyexemplary of a preferred embodiment and that the invention is equallyapplicable to other configurations, for example utilizing batteries witha different form factor, a larger or smaller number of cells, individualcells versus modules, different cell chemistries, etc.

As noted above, the present invention does not rely on a particularimplementation of the battery pack enclosure and more specifically, doesnot rely on a particular implement of the batteries and battery modulesthat are contained within the battery pack enclosure. Specificimplementations of both are only provided herein to illustrate onepreferred configuration. FIG. 8 provides a perspective view of a singlemodule 701, this view highlighting the module mounting flange 801. Inthis configuration, mounting flanges 801 are located on either side ofthe module and, during battery pack assembly, are captured between upperand lower sections of each cross-member. FIG. 9 shows the previouslyillustrated battery module with the upper portion of module 701 removedas well as several of the upper module components (e.g., cell locatorplate, current collector plate, etc.), thus making the individual cells901 visible. Note that the orientation of cells 901 within module 701varies. FIG. 10 provides a similar view to that of FIG. 9, with theexception that cells 901 have been removed. With the removal of cells901, the cooling conduits 1001 are visible, conduits 1001 being coupledto the battery pack thermal management system (not shown).

FIG. 11 provides a perspective, cross-sectional view of battery pack 101mounted under floor panel 403 of vehicle 100. This view also providesadditional views of the cross-members. Note that in this figure thebatteries/battery modules are not shown within the battery pack, thussimplifying the figure in order to better illustrate the basic batterypack/vehicle assembly.

As shown in the cross-sectional view of FIG. 11, preferablycross-members 601A-601H do not utilize the same cross-section; ratherthe cross-section of each is optimized for that particular member'slocation within the pack. In general, cross-members 601A-601H may eitherbe comprised of a single unit or as preferred, comprised of an uppersection and a lower section, thus providing a convenient means ofcapturing and mounting the battery modules 701. One or both sections ofeach cross-member may be hollow, thus minimizing weight while stillproviding a rigid and strong structural member. It should be understoodthat not only can the configuration/design of the cross-members vary,depending upon their location within the pack, so can the materialscomprising the cross-members. Therefore while cross-members 601A-601Hare preferably fabricated from aluminum or an aluminum alloy, forexample using an extrusion process, other materials (e.g., steel,ceramics, etc.) may also be used if such materials fit both themechanical and thermal goals for the particular cross-member inquestion. Additionally, the lumens within one or more of thecross-members may be unfilled or filled, for example filled with a highmelting temperature, low thermal conductivity material (e.g., fiberglassor similar material). Alternately, the lumens within the cross-membersmay include a liquid (e.g., water), the liquid being either stagnant orflowing. If stagnant, the liquid may be contained within the lumensthemselves or, as preferred, contained within pouches that fit withinthe cavities. If the liquid is flowing, it is preferably containedwithin tubing that is inserted within the cross-member cavities andeither coupled to a battery cooling system or used in a stand-alonecirculation system.

Preferably and as illustrated in FIG. 11, cross-members 601D and 601Eare larger than the other central cross-members. The reason for theincreased size for these particular cross-members is to provideadditional cross-member strength at those locations that are mostcritical to resisting side impact loads that may be encountered during acollision.

FIG. 12 provides a detailed cross-sectional view of a portion of batterypack 101 along with the structures immediately above and below thebattery pack enclosure. Note that due to the plane used for purposes ofthis cross-section, and due to the staggering of batteries in thisembodiment as illustrated in FIG. 9, the cells mounted to the left sideof each cooling conduit 1001 are not visible in this figure.

FIG. 12 shows two of the primary aspects of the invention; an upperinsulating layer 1201 interposed between the upper surface of batterypack 101 and the vehicle floor panel 403, and a lower ballistic shield1203 located between the lower surface of battery pack 101 and the roadsurface. Each of these components is discussed separately below as theymay be used alone, or together, for an under floor mounted battery pack.Note that in the configuration shown in FIGS. 12-15, module mountingflanges 801 are shown captured between a cross-member upper section 1205and a cross-member lower section 1207, the upper and lower sectionsproviding a simple means of locating and holding the module in placewithin the battery pack.

Battery Pack Upper Insulating Layer

As described in detail below, preferably layer 1201 is a multi-purposelayer that dramatically enhances passenger comfort by providing noiseisolation and damping vibrations that might otherwise pass into thepassenger cabin. Preferably layer 1201 also acts as a thermal barrierbetween battery pack 101 and floor panel 403, and therefore betweenbattery pack 101 and the passenger compartment. It should be understoodthat while a single layer is shown in FIGS. 12, 14 and 15, layer 1201may actually be comprised of multiple layers as illustrated in FIG. 13,thus allowing each layer to be targeted and optimized for a specificpurpose.

While the bulk of the battery pack enclosure, including the variouscomponents within the battery pack, help to isolate the passengercompartment from road noise and other external noises, it will beappreciated that many noises pass through, or are transmitted by,battery pack 101. Accordingly, in the preferred embodiment layer 1201 isused to prevent noise intrusion into and through vehicle flooring 403.Preferably layer 1201 provides an acoustic insertion loss of greaterthan 10 dB, and more preferably greater than 20 dB, for frequenciesabove 1000 Hz in general, and for frequencies between 1000 Hz and 10 kHzin particular.

In addition to providing sound isolation, preferably layer 1201 alsoprovides vibration damping. Preferably layer 1201 has a damping lossfactor of at least 0.1 (10%), more preferably at least 0.25 (25%), stillmore preferably at least 0.3 (30%), and yet still more preferably atleast 0.4 (40%).

Layer(s) 1201 also provides thermal isolation, specifically isolatingthe passenger cabin from heat generated by the batteries within batterypack 101 and helping to insure that the batteries are allowed to operatewithin the preferred temperature range regardless of the temperaturewithin the passenger cabin. Preferably layer 1201 is designed to isolatethe passenger cabin during normal vehicle operation, thus insuringpassenger comfort, and in the event of the occurrence of thermal runawaywithin the pack, thus insuring passenger safety. In a preferredembodiment, layer 1201 exhibits low thermal conductivity while beingresistant to high temperatures. For example, in one embodiment layer1201 has a thermal conductivity of less than 0.25 W/m-K, preferably lessthan 0.2 W/m-K, more preferably less than 0.15 W/m-K, and still morepreferably less than 0.1 W/m-K. In one embodiment layer 1201 is capableof withstanding temperatures of more than 500° C. continuously,preferably capable of withstanding temperatures of more than 750° C.continuously and/or withstanding temperatures of more than 1000° C. fora period of at least 10 seconds, more preferably capable of withstandingtemperatures of more than 900° C. continuously and/or withstandingtemperatures of more than 1000° C. for a period of at least 10 seconds,and still more preferably capable of withstanding temperatures of morethan 1000° C. continuously and/or withstanding temperatures of more than1400° C. for a period of at least 1 second.

In order to meet the goals stated above, especially insertion anddamping loss, the inventors have found that layer or layers 1201 must becompressed, preferably on the order of 30%. Additionally, by compressinglayer 1201, a strong mechanical coupling between floor panel 403 and therigid battery pack structure is achieved, allowing the rigidity of thebattery pack enclosure to augment the stiffness of the floor panel,thereby providing a stiffer flooring for the passenger cabin than wouldotherwise be achieved for the same thickness floor panel.

In one embodiment, layer 1201 is comprised of a 6 millimeter blanketwhich is compressed down to approximately 4 millimeters when the batterypack 101 is mounted to the vehicle's underbody. For this amount ofcompression, the compression modulus of the material is preferably lowenough to allow layer 1201 to “flow” into all of the features of thevehicle's floor panel 403 and top panel 501 of the battery pack. Inaddition, a relatively soft material is needed to allow for assemblysince even a low modulus material can exert a large force duringcompression given the very large surface area of battery pack 101. In atleast one embodiment, a compression modulus of 1.5 PSI at 25%compression is preferred, this value typically referred to as thematerial's CLD (i.e., compression load deflection).

In one preferred embodiment, layer 1201 is comprised of a compressibleceramic fiber sheet, for example one fabricated from a weave of silicaand calcium oxide fibers held together with a binder (e.g., an organicbinder). Alternate exemplary materials suitable to fabricate layer 1201include silica/silica fibers, alumina, Kevlar®, Nomex® andcalcium-magnesium-silicate fibers.

In an alternate preferred embodiment, layer 1201 is comprised of twolayers 1301/1302 as illustrated in FIG. 13. Layer 1301, preferablylocated adjacent to the underside of floor panel 403, is comprised of alow modulus, highly conformable foam. Layer 1302, preferably locatedadjacent to the top panel of battery pack 101, is comprised of a ceramicfiber sheet. In an exemplary embodiment, layer 1301 is approximately 3millimeters thick and comprised of a closed cell foam urethane sheet andlayer 1302 is approximately 6 millimeters thick and comprised of silicaand calcium oxide fibers held together with a binder.

Battery Pack Lower Ballistic Shield

Although battery pack enclosure 101 is designed to protect the batteriescontained therein, due to the location of battery pack 101 under thefloor panel of the vehicle it is possible for road debris to impact thelower surface 603 of the battery pack with sufficient force to dent anddeform it and potentially damage cells 901 or the cell interconnects,cooling conduits, etc. Accordingly, in at least one embodiment anadditional ballistic shield 1203 is mounted below and at some distancefrom pack 101, thereby providing another level of protection. It shouldbe understood that the inclusion of a lower ballistic shield isindependent of the inclusion of one or more layers between the batterypack and the floor panel (e.g., layer 1201, layers 1301/1302) andtherefore a vehicle may use one, or both, innovations.

In order to prevent road debris that impacts shield layer 1203 fromtransferring that impact force directly into the lower surface 603 ofthe battery pack 101, layer 1203 is spaced apart from pack 101. As aresult, when an object impacts layer 1203, the battery pack enclosureremains undamaged even if layer 1203 is deformed. Typically ballisticshield 1203 is spaced at least 10 millimeters from lower battery packsurface 603, preferably at least 15 millimeters from lower battery packsurface 603, more preferably at least 25 millimeters from lower batterypack surface 603, still more preferably at least 35 millimeters fromlower battery pack surface 603, and yet still more preferably at least50 millimeters from lower battery pack surface 603.

Shield layer 1203 is formed of a relatively light-weight material, suchas a light-weight metal (e.g., aluminum, aluminum alloy, etc.) or acomposite such as a carbon fiber/epoxy composite. Alternately, layer1203 may be comprised of fiberglass or a plastic (e.g., polyethylene,polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene,etc.).

Ballistic shield layer 1203 may be mounted directly to the underside ofvehicle 101 or, via stand-offs, to the underside of battery pack 101.Regardless of whether the perimeter of shield 1203 is mounted to thevehicle undercarriage or to the battery pack, preferably a plurality ofstand-offs are used to hold layer 1203 apart from the underside ofbattery pack 101. The stand-offs, represented by stand-off 1205 in thefigures, adds rigidity to shield 1203 while still allowing it to berelatively thin. Preferably the stand-offs are located adjacent to across-member, as shown, thus helping to prevent an impact at thelocation of the stand-off from deforming the battery pack and thecomponents contained therein.

In a modification of the shield configuration described above, a layer1401 of a compressible material is interposed between the bottom 603 ofpack 101 and shield 1203. Although layer 1401 may be used in conjunctionwith stand-offs 1205, preferably layer 1401 acts as a replacement forthe stand-offs as illustrated in FIG. 14. In addition to dampingvibrations during normal vehicle operation, layer 1401 also damps anddistributes impact energy when an object impacts shield 1203, therebyproviding another level of protection for battery pack 101. Preferablylayer 1401 is fabricated from a compressible material that is easilydeformed. The deformation of the compressible material may be elastic orinelastic. In one embodiment layer 1401 is fabricated from a plastic,for example using injection molding. In an alternate embodiment layer1401 is fabricated from foam (e.g., a closed cell urethane foam).

FIG. 15 illustrates a modification of the embodiment shown in FIG. 14.As shown, the layer 1501 that is interposed between pack 101 and shield1203 is shaped to include a plurality of projections (e.g., fingers orbumps) 1503 that contact both surface 603 and shield 1203, and aplurality of dips 1505 that only contact one of the two surface (e.g.,either bottom pack layer 603 as shown or ballistic shield layer 1203).An exemplary design for layer 1501 utilizes the shape commonly referredto as “egg crate shaped”.

It should be understood that identical element symbols used on multiplefigures refer to the same component, or components of equalfunctionality. Additionally, the accompanying figures are only meant toillustrate, not limit, the scope of the invention and should not beconsidered to be to scale.

Systems and methods have been described in general terms as an aid tounderstanding details of the invention. In some instances, well-knownstructures, materials, and/or operations have not been specificallyshown or described in detail to avoid obscuring aspects of theinvention. In other instances, specific details have been given in orderto provide a thorough understanding of the invention. One skilled in therelevant art will recognize that the invention may be embodied in otherspecific forms, for example to adapt to a particular system or apparatusor situation or material or component, without departing from the spiritor essential characteristics thereof. Therefore the disclosures anddescriptions herein are intended to be illustrative, but not limiting,of the scope of the invention which is set forth in the followingclaims.

1. A vehicle battery pack protection system, comprising: a battery packenclosure mounted under an electric vehicle, wherein said battery packenclosure comprises an enclosure top panel, an enclosure bottom panel,and a plurality of enclosure side members, wherein said battery packenclosure is configured to hold a plurality of batteries, and whereinsaid battery pack enclosure is mounted between a passenger cabin floorpanel and a driving surface; a ballistic shield mounted under saidelectric vehicle and below said battery pack enclosure, wherein saidballistic shield is interposed between said battery pack enclosure andsaid driving surface, and wherein said ballistic shield is spaced apartfrom said enclosure bottom panel by at least 5 millimeters; and aplurality of stand-offs, wherein said plurality of stand-offs areinterposed between said ballistic shield and said enclosure bottompanel.
 2. The vehicle battery pack protection system of claim 1, whereinsaid battery pack enclosure is substantially airtight.
 3. The vehiclebattery pack protection system of claim 1, wherein said enclosure toppanel, said enclosure bottom panel, and said plurality of enclosure sidemembers are each fabricated from a material selected from the group ofmaterials consisting of aluminum, aluminum alloys and steel.
 4. Thevehicle battery pack protection system of claim 1, wherein saidenclosure bottom panel is welded, brazed, soldered or bonded to saidplurality of enclosure side members, and wherein said enclosure toppanel is bolted to said plurality of enclosure side members.
 5. Thevehicle battery pack protection system of claim 1, wherein said batterypack enclosure is mounted between a first vehicle structural side memberlocated adjacent to a first side of said vehicle and a second vehiclestructural side member located adjacent to a second side of saidvehicle, wherein said battery pack enclosure is mounted between a frontvehicle suspension assembly and a rear vehicle suspension assembly,wherein said battery pack enclosure transverses the distance betweensaid first vehicle structural side member and said second vehiclestructural side member, wherein a first side member of said plurality ofenclosure side members is mechanically coupled to said first vehiclestructural side member and a second side member of said plurality ofenclosure side members is mechanically coupled to said second vehiclestructural side member, wherein said battery pack enclosure furthercomprises a plurality of cross-members integrated into said battery packenclosure, wherein each of said plurality of cross-members transversesthe distance between said first and second side members of said batterypack enclosure, and wherein said plurality of cross-members segregatesaid plurality of batteries into groups of batteries.
 6. The vehiclebattery pack protection system of claim 5, wherein said first vehiclestructural side member is a left side rocker panel, and wherein saidsecond vehicle structural side member is a right side rocker panel. 7.The vehicle battery pack protection system of claim 1, wherein saidballistic shield is spaced apart from said enclosure bottom panel by atleast 10 millimeters.
 8. The vehicle battery pack protection system ofclaim 1, wherein said ballistic shield is spaced apart from saidenclosure bottom panel by at least 15 millimeters.
 9. The vehiclebattery pack protection system of claim 1, wherein said ballistic shieldis spaced apart from said enclosure bottom panel by at least 25millimeters.
 10. The vehicle battery pack protection system of claim 1,wherein said ballistic shield is spaced apart from said enclosure bottompanel by at least 35 millimeters.
 11. The vehicle battery packprotection system of claim 1, wherein said ballistic shield is spacedapart from said enclosure bottom panel by at least 50 millimeters. 12.The vehicle battery pack protection system of claim 1, wherein saidballistic shield is comprised of a material selected from the group ofmaterials consisting of aluminum, aluminum alloys, steel, fiberglass,carbon fiber/epoxy composites, and plastic.
 13. A vehicle battery packprotection system comprising: a battery pack enclosure mounted under anelectric vehicle, wherein said battery pack enclosure comprises anenclosure to panel an enclosure bottom panel, and a plurality ofenclosure side members, wherein said battery pack enclosure isconfigured to hold a plurality of batteries, wherein said battery packenclosure is mounted between a passenger cabin floor panel and a drivingsurface, wherein said battery pack enclosure is mounted between a firstvehicle structural side member located adjacent to a first side of saidvehicle and a second vehicle structural side member located adjacent toa second side of said vehicle, wherein said battery pack enclosure ismounted between a front vehicle suspension assembly and a rear vehiclesuspension assembly, wherein said battery pack enclosure transverses thedistance between said first vehicle structural side member and saidsecond vehicle structural side member, wherein a first side member ofsaid plurality of enclosure side members is mechanically coupled to saidfirst vehicle structural side member and a second side member of saidplurality of enclosure side members is mechanically coupled to saidsecond vehicle structural side member, wherein said battery packenclosure further comprises a plurality of cross-members integrated intosaid battery pack enclosure, wherein each of said plurality ofcross-members transverses the distance between said first and secondside members of said battery pack enclosure, and wherein said pluralityof cross-members segregate said plurality of batteries into groups ofbatteries; a ballistic shield mounted under said electric vehicle andbelow said battery pack enclosure, wherein said ballistic shield isinterposed between said battery pack enclosure and said driving surface,and wherein said ballistic shield is spaced apart from said enclosurebottom panel at least 5 millimeters; and a plurality of stand-offs,wherein said plurality of stand-offs are interposed between saidballistic shield and said enclosure bottom panel, and wherein saidplurality of stand-offs are coupled to an outer surface of saidenclosure bottom panel adjacent to mounting locations of said pluralityof cross-members mounted to an inner surface of said enclosure bottompanel.
 14. The vehicle battery pack protection system of claim 13,wherein said enclosure top panel, said enclosure bottom panel, and saidplurality of enclosure side members are each fabricated from a materialselected from the group of materials consisting of aluminum, aluminumalloys and steel.
 15. The vehicle battery pack protection system ofclaim 13, wherein said enclosure bottom panel is welded, brazed,soldered or bonded to said plurality of enclosure side members, andwherein said enclosure top panel is bolted to said plurality ofenclosure side members.
 16. The vehicle battery pack protection systemof claim 13, wherein said first vehicle structural side member is a leftside rocker panel, and wherein said second vehicle structural sidemember is a right side rocker panel.
 17. The vehicle battery packprotection system of claim 13, wherein said ballistic shield is spacedapart from said enclosure bottom panel by at least 10 millimeters. 18.The vehicle battery pack protection system of claim 13, wherein saidballistic shield is spaced apart from said enclosure bottom panel by atleast 25 millimeters.
 19. The vehicle battery pack protection system ofclaim 13, wherein said ballistic shield is spaced apart from saidenclosure bottom panel by at least 50 millimeters.
 20. The vehiclebattery pack protection system of claim 13, wherein said ballisticshield is comprised of a material selected from the group of materialsconsisting of aluminum, aluminum alloys, steel, fiberglass, carbonfiber/epoxy composites, and plastic.